Zygolophodon

{{Short description|Extinct genus of mammutid proboscidean}} {{Automatic taxobox | fossil_range = {{fossilrange|Early Miocene|Late Miocene}} | image = Zygolophodon skull fossil.jpg | image_caption = Skull of ''Zygolophodon'' sp. from Laogou, Gansu Province, China | image2 = Zygolophodon turicensis molars.jpg | image2_caption = Molars of ''Zygolophodon turicensis'' | taxon = Zygolophodon | authority = Vacek, 1877 | type_species = †'''''Mastodon turicensis''''' | type_species_authority = (Schinz, 1824) | subdivision_ranks = Species | subdivision = *''Z. aegyptensis'' Sanders & Miller, 2002 *''Z. atavus'' Borissiak, 1936 *''Z. gobiensis'' Osborn & Granger, 1932 *''Z. metachinjiensis'' Osborn, 1929 *''Z. microgigas'' Sanders, 2026 *''Z. proavus'' Cope, 1873 *''Z. turicensis'' Schintz, 1824 '''Possibly valid species:''' *''Z. chinjiensis'' Chow & Chang, 1978 *''Z. lufengensis'' Zhang, 1982 *''Z. nemonguensis'' Chow & Chang, 1961 | range_map = | range_map_caption = | synonyms = {{species list |''Mastodon proavus''|Cope, 1873 |''Mastodon tapiroides''|Cuvier, 1824 |''Mastodon turicensis''|Schnitz, 1824 |''Mammut tapiroides''|Cuvier, 1824 |''Mammut turicensis''|Schnitz, 1824 |hidden=yes}} }}

'''''Zygolophodon''''' is an extinct genus of mammutid proboscidean that lived during the Miocene in Africa, Eurasia, and North America.<ref>{{cite journal|last=Youping, Yuzhu, Hongxiang, Suyin|first=Zhang, Long, Ji, Ding|orig-year=March 1989|date= November 1999|title=The Cenozoic Deposits of the Yunnnan Region (Institute of Vertebrate Paleontology, Paleoanthropology Academia Sinica)|url=http://paleoglot.org/files/Zhang&_83.pdf|journal=Professional Papers on Stratigraphy and Paleontology, No. 7 Geological Publishing House, Peking, China, Pp. 1-21}}</ref> It is suggested to be ancestral to ''Mammut'', the genus containing the American mastodons.

== Description == [[File:"Mammut" borsoni foot and leg diagram.png|left|thumb|Foot of ''"Mammut" borsoni'' (left) and the forelimb anatomy of ''Zygolophodon turicensis'' (B), compared to ''"Mammut" borsoni'' (C) and the American mastodon (''Mammut americanum'') (D)]] [[File:Zygolophodon proavus lower jaw.svg|left|thumb|Lower jaw of the "Unity" specimen of ''Zygolophodon proavus'' (OMSI 1946.02.1026), showing elongate mandibular symphysis and lower tusks]] As with other mammutids, the molars have a zygodont morphology. As is typical for early members of Elephantimorpha, the fused front region of the lower jaw (the mandibular symphysis) is primitively elongate and bears tusks/incisors, similar to ''Gomphotherium'', as exhibited in specimens of species like ''Z. proavus'', but in some individuals of ''Z. turicensis'', the front part of the lower jaw is short and sometimes in addition lacks lower tusks.<ref name="Mothe16">{{Cite journal |last1=Mothé |first1=Dimila |last2=Avilla |first2=Leonardo S. |last3=Zhao |first3=Desi |last4=Xie |first4=Guangpu |last5=Sun |first5=Boyang |last6=Mothé |first6=Dimila |last7=Avilla |first7=Leonardo S. |last8=Zhao |first8=Desi |last9=Xie |first9=Guangpu |year=2016 |title=A new Mammutidae (Proboscidea, Mammalia) from the Late Miocene of Gansu Province, China |journal=Anais da Academia Brasileira de Ciências |volume=88 |issue=1 |pages=65–74 |doi=10.1590/0001-3765201520150261 |issn=0001-3765 |pmid=26839998 |doi-access=free}}</ref><ref name=":3" /> The upper tusks have enamel bands and are untwisted and downward curving, and outwardly diverge from each other.<ref>{{Cite report |url=https://www.researchsquare.com/article/rs-3046011/v1 |title=First true mastodon from the Late Miocene of Western Asia |last1=Yaghoubi |first1=Sadaf |last2=Ashouri |first2=Ali Reza |date=2023-07-05 |publisher=In Review |doi=10.21203/rs.3.rs-3046011/v1 |last3=Ataabadi |first3=Majid Mirzaie |last4=Ghaderi |first4=Abbas|doi-access=free }}</ref> The jaws retained permanent premolar teeth.<ref>{{Cite journal |last=Sanders |first=William J. |date=2018-02-17 |title=Horizontal tooth displacement and premolar occurrence in elephants and other elephantiform proboscideans |url=https://www.tandfonline.com/doi/full/10.1080/08912963.2017.1297436 |journal=Historical Biology |language=en |volume=30 |issue=1–2 |pages=137–156 |doi=10.1080/08912963.2017.1297436 |bibcode=2018HBio...30..137S |s2cid=89904463 |issn=0891-2963|url-access=subscription }}</ref> Species probably reached similar sizes to the American mastodon, with a shoulder height of {{Convert|2.5-3|m}} estimated for the species ''Z. metachinjiensis.''<ref name=":6">{{Cite book |last1=Tassy |first1=Pascal |url=https://www.press.jhu.edu/books/title/11911/foot-himalayas |title=At the Foot of the Himalayas: Paleontology and Ecosystem Dynamics of the Siwalik Record |last2=Sanders |first2=William J. |date=2025 |publisher=Johns Hopkins University Press |isbn=978-1-4214-5027-8 |editor-last=Badgley |editor-first=Catherine |pages=250–251 |language=en |chapter=Siwalik Proboscidea |editor-last2=Morgan |editor-first2=Michèle E. |editor-last3=Pilbeam |editor-first3=David}}</ref>

== Ecology == [[File:Miomastodon proavusDB.jpg|thumb|Life restoration of ''Zygolophodon proavus,'' the likely ancestor of the American mastodons (''Mammut'')]] ''Zygolophodon'' is suggested to have primarily had a browsing-based diet.<ref>{{Cite journal |last=Janis |first=C |date=May 2004 |title=The species richness of Miocene browsers, and implications for habitat type and primary productivity in the North American grassland biome |url=https://linkinghub.elsevier.com/retrieve/pii/S0031018204000483 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |language=en |volume=207 |issue=3–4 |pages=371–398 |doi=10.1016/j.palaeo.2003.09.032|bibcode=2004PPP...207..371J |url-access=subscription }}</ref><ref name=":6" /> Its teeth primarily served to vertically chew plant material.<ref name=":6" />

==Taxonomy and evolution== ''Zygolophodon'' belongs in the family Mammutidae, whose best known member is the American mastodon (''Mammut americanum'').<ref name=":6" /> Due to the conservatism of tooth morphology in ''Zygolophodon'' and the fact that most species are only or mostly known from molar teeth, is it difficult to determine the true number of valid species.<ref name=":6" />

The genus likely originated in Africa. The oldest species is ''Z. aegyptensis,'' known from Egypt and Namibia, dating to the late Early Miocene-early Middle Miocene.<ref>{{cite journal | last1=Sanders | first1=William J. | last2=Miller | first2=Ellen R. | title=New Proboscideans from the Early Miocene of Wadi Moghara, Egypt | journal=Journal of Vertebrate Paleontology | date=2002 | volume=22 | issue=2 | pages=388–404 | doi=10.1671/0272-4634(2002)022[0388:NPFTEM]2.0.CO;2 | jstor=4524231 | url=https://www.jstor.org/stable/4524231 }}</ref><ref name=":0">{{cite journal | last1=Duangkrayom | first1=Jaroon | last2=Wang | first2=Shi-Qi | last3=Deng | first3=Tao | last4=Jintasakul | first4=Pratueng | title=The first Neogene record of ''Zygolophodon'' (Mammalia, Proboscidea) in Thailand: Implications for the mammutid evolution and dispersal in Southeast Asia | journal=Journal of Paleontology | date=2017 | volume=91 | issue=1 | pages=179–193 | doi=10.1017/jpa.2016.143 | bibcode=2017JPal...91..179D }}</ref> The species ''Z. turicensis'' had a widespread distribution in both Africa (Kenya, Tunisia), Anatolia and Europe, dating to the Early-Late Miocene,<ref>{{Cite journal |last1=Erten |first1=Hüseyin |last2=Koralay |first2=Demet Banu |date=December 2020 |title=A Zygolophodon turicensis (Proboscidea, Mammalia) mandible fragment from the Kale-Tavas basin (Denizli, Turkey) |url=https://link.springer.com/10.1007/s12549-020-00422-7 |journal=Palaeobiodiversity and Palaeoenvironments |language=en |volume=100 |issue=4 |pages=1077–1082 |doi=10.1007/s12549-020-00422-7 |bibcode=2020PdPe..100.1077E |s2cid=215741701 |issn=1867-1594|url-access=subscription }}</ref><ref name=":0" /> with its earliest appearance in Europe being approximately 18-17 million years ago,<ref name=":2" /> and last appearance in the region dating to around 7-6 million years ago.''<ref name=":12">{{Cite journal |last1=Mazo |first1=A.V. |last2=Van der Made |first2=J. |date=March 2012 |title=Iberian mastodonts: Geographic and stratigraphic distribution |url=https://linkinghub.elsevier.com/retrieve/pii/S1040618211004472 |journal=Quaternary International |language=en |volume=255 |pages=239–256 |doi=10.1016/j.quaint.2011.07.047|bibcode=2012QuInt.255..239M |url-access=subscription }}</ref>'' The youngest confirmed record of ''Zygolophodon'' in Africa dates to around 13 million years ago, based on teeth suggested to belong to ''Z. turicensis'' found in Kenya, though a possible younger record is known from the Late Miocene of Algeria.<ref>Pickford, M. 2007. [https://wiredspace.wits.ac.za/bitstream/handle/10539/17292/Pal-Vol-42.pdf#page=31 New mammutid proboscidean teeth from the middle Miocene of tropical and southern Africa]. ''Palaeontologia Africana'' 42: 29–35.</ref>

The species ''Z''. ''tapiroides'' (Desmarets, 1822) is considered invalid''.<ref name=":0" /><ref name=":1" />'' The taxonomy of East Asian ''Zygolophodon'' is uncertain. Tassy ''et al.'' (1988) synonymised many Chinese species with ''Z. gobiensis'' (including ''Z. lufengensis'', ''Z. chinjiensis'', ''Z. nemonguensis'', ''Z. gromovae'' and ''Z. jiningensis,'' as well as ''Miomastodon tongxiensis''), with ''Z. gobiensis'' also known from Mongolia, but other authors suggest that at least some of these species may be valid.<ref name=":0" /> The species ''Z. atavus'' is known from the early Middle Miocene of Kazakhstan.<ref name=":0" /> The oldest remains of ''Zygolophodon'' on the Indian subcontinent are known from the Bugti Hills of Pakistan, dating to around 19-17 million years ago. The species ''Z. metachinjiensis'' is known from the mid-Late Miocene (around 13.8 to 12.4 million years ago<ref name=":6" />) of Pakistan.<ref name=":5" /> ''Zygolophodon'' has also been reported from western India, dating to the mid Miocene,<ref>{{Cite journal |last1=Kapur |first1=Vivesh V |last2=Pickford |first2=Martin |last3=Chauhan |first3=Gaurav |last4=Thakkar |first4=M.G. |date=2021-05-04 |title=A Middle Miocene (~14 Ma) vertebrate assemblage from Palasava, Rapar Taluka, Kutch (Kachchh) District, Gujarat State, western India |url=https://www.tandfonline.com/doi/full/10.1080/08912963.2019.1648451 |journal=Historical Biology |language=en |volume=33 |issue=5 |pages=595–615 |doi=10.1080/08912963.2019.1648451 |bibcode=2021HBio...33..595K |s2cid=202008961 |issn=0891-2963|url-access=subscription }}</ref> and other probable remains dating to the Late Miocene, around 10 million years old, representing the youngest mammutids on the Indian subcontinent.<ref name=":5">{{Cite journal |last1=Choudhary |first1=Deepak |last2=Jukar |first2=Advait M. |last3=Patnaik |first3=Rajeev |last4=Singh |first4=Nongmaithem Amardas |last5=Singh |first5=Ningthoujam Premjit |last6=Milankumar Sharma |first6=K. |date=2022-10-28 |title=The first report of cf. Zygolophodon (Mammalia, Proboscidea, Mammutidae) from the Upper Miocene of Kutch, India |url=https://www.tandfonline.com/doi/full/10.1080/02724634.2023.2197959 |journal=Journal of Vertebrate Paleontology |language=en |volume=42 |issue=4 |article-number=e2197959 |doi=10.1080/02724634.2023.2197959 |bibcode=2022JVPal..42E7959C |s2cid=258338571 |issn=0272-4634|url-access=subscription }}</ref> An indeterminate species has also been reported from Thailand, of uncertain but probably Late Miocene age.<ref name=":0" /> [[File:Zygolophodon turicensisDB.jpg|thumb|Life restoration of ''Z. turicensis'' with a shortened (brevirostrine) lower jaw. ''Z. turicensis'' is suggest to be the ancestor of ''"Mammut" borsoni'', one of the largest land mammals ever]] ''Zygolophodon'' entered North America during the latter part of the Early Miocene (during the late Hemingfordian faunal stage), with the oldest record being a partial tooth from Massacre Lake, Nevada, dating to 16.5-16.4 million years ago.<ref name=":3">{{Cite journal |last1=Koenigswald |first1=W. von |last2=Widga |first2=C. |last3=Gohlich |first3=U. B. |date=May 2023 |title=New mammutids (Proboscidea) from the Clarendonian and Hemphillian of Oregon - a survey of Mio-Pliocene mammutids from North America |url=https://hdl.handle.net/1794/29306 |journal=Bulletin of the Museum of Natural History, University of Oregon |hdl=1794/29306 |language=en-US}}</ref> Remains of ''Zygolophodon'' are known from across western and central North America during the following Barstovian (including Colorado, California, Montana, Oregon, Nebraska, Nevada, Wyoming and Saskatchewan). ''Z. proavus'' currently represents the only known North American species of ''Zygolophodon.''<ref name=":1">{{Cite journal |last1=Lofgren |first1=Don L. |last2=Anand |first2=Rajsavi S. |date=November 2011 |title=Partial skull of Zygolophodon (Mammalia, Proboscidea) from the Barstow Formation of California |url=http://www.tandfonline.com/doi/abs/10.1080/02724634.2011.605192 |journal=Journal of Vertebrate Paleontology |language=en |volume=31 |issue=6 |pages=1392–1396 |doi=10.1080/02724634.2011.605192 |bibcode=2011JVPal..31.1392L |s2cid=86845027 |issn=0272-4634|url-access=subscription }}</ref><ref name=":3" /> The youngest specimens of ''Z''. ''proavus'' date to approximately 11-12 million years ago.<ref name=":3" /> The genus ''Mammut,'' containing the American mastodons, is thought to be descended from ''Zygolophodon,'' most likely ''Z. proavus''. The gigantic Eurasian species ''"Mammut" borsoni,'' which is suggested to most likely descend from ''Z. turicensis'', is the youngest member of Mammutidae in Eurasia, persisting from the Late Miocene into the Earliest Pleistocene, around 2.5-2 million years ago. ''"M." borsoni'' has sometimes been placed in ''Zygolophodon,'' though its taxonomic placement is controversial.<ref name=":2">{{Cite journal |last1=Koenigswald |first1=Wighart |last2=Březina |first2=Jakub |last3=Werneburg |first3=Ralf |last4=Göhlich |first4=Ursula |date=2022 |title=A partial skeleton of "Mammut" borsoni (Proboscidea, Mammalia) from the Pliocene of Kaltensundheim (Germany) |url=https://palaeo-electronica.org/content/2022/3573-mammut-kaltensundheim |journal=Palaeontologia Electronica |volume=25 |issue=1 |pages=1–45 |doi=10.26879/1188|s2cid=247374131 |doi-access=free }}</ref>

Some authors have suggested placing ''M. tongxinensis'', ''Z.'' ''gobiensis'' and ''Z. metachinjiensis'' within a revived ''Miomastodon'', which was originally described for the North American ''Miomastodon merriami.''<ref name=":4">Wang, S.-Q., Zhang, X.-X., and Li, C.-Y. 2020. [https://www.researchgate.net/publication/340643777_Reappraisal_of_Serridentinus_gobiensis_Osborn_Granger_and_Miomastodon_tongxinensis_Chen_the_validity_of_Miomastodon Reappraisal of ''Serridentinus gobiensis'' Osborn and Granger and ''Miomastodon tongxinensis'' Chen: The Validity of Miomastodon]. Vertebrate PalAsiatica, 58:134-158.</ref> ''Miomastodon'' is usually treated as a synonym of ''Zygolophodon'' (with ''M. merriami'' typically considered a synonym of ''Z. proavus'')''<ref name=":1" />'' and other authors have reacted with caution to the proposal.<ref name=":2" />

== External links ==

* [https://www.morphosource.org/concern/media/000116784?locale=en Rotatable 3D model of the skull and lower jaws of the "Unity" specimen ''Zygolophodon proavus'' on MorphoSource]

== References == {{Reflist}}

Category:Mammutidae Category:Miocene proboscideans Category:Pliocene proboscideans Category:Miocene mammals of North America Category:Miocene mammals of Asia Category:Miocene mammals of Europe Category:Pliocene mammals of North America Category:Pliocene mammals of Asia Category:Pliocene mammals of Europe Category:Miocene mammals of Africa Category:Pliocene mammals of Africa Category:Prehistoric placental genera Category:Fossil taxa described in 1877